As known to all, mechanical gear apparatuses have been applied widely in the industry field. It's not hard to find out that mechanical gears are composed of a plurality of individual moving elements, and the power transmission between the a plurality of moving elements is achieved by the engagement of teeth arranged on peripheries of the moving elements. Therefore, the contact between the moving elements of the mechanical gears will definitely bring a plurality of troubles such as friction loss, vibration, noise, lubrication requirement and periodical maintenance requirement. Mechanical gears are severely limited in circumstances concerning fluid-flow control, such as in an artificial blood pump or a poison gas pipe pump, because the mechanical gears cannot realize complete isolation between the output end and the input end. Thus, there may often be the hidden danger of fluid leakage, and the failure of sealing measure will bring severe result. In industry application, there exist many occasions which require speed changes, and giant mechanical gear boxes are generally required to meet the requirements. A giant gear box will unavoidably increase the volume and weight of a system, and improve the complexity of the system. Furthermore, the mechanical gears are engaged with each other rigidly with teeth, once the torque is beyond the affordability force, security accidents are likely to happen.
Magnetic transmission apparatus is also known as magnetic gear, which is a new transmission technology. The magnetic transmission apparatus utilizes the magnetic fields of permanent magnets to transmit force or torque, since there is no contact action between the magnet fields of the permanent magnets, contactless transmission of force or torque can be achieved. Compared with mechanical gear, the advantages of magnetic transmission apparatus are: (1) the output end and input end being completely isolated; (2) better sealing compared with mechanical gear; (3) over protection capacity; (4) being able to help soft start the engine; (5) no noise; (6) no periodical maintenance. The magnetic gear can remedy the deficiency of the mechanical gear, and has been applied in a plurality of transmission circumstances.
The current magnetic gears can be classified into direct coupled type magnetic gears and magnetic field modulated type magnetic gears. The direct coupled type magnetic gears generally transmit force or torque by imitating the mechanical gears. The magnetic field of the permanent magnets of the direct couple type magnetic gears possesses a pretty low degree of coupling; therefore, the torque density thereof is lower than that of the mechanical gear. Magnetic field modulated type magnetic gears generally refer to coaxial magnetic gears which utilize iron cores to modulate the magnetic field formed by the permanent magnets, thereby forming plenty of magnetic field harmonics, and achieving speed changes and transmissions of force or torque through the interaction of the magnetic harmonics. The magnetic gears take full advantage of the magnetic field excited by the permanent magnets, and improve the torque density of the magnetic gear greatly. With the development of the material of permanent magnets, torque density of the magnetic gears has improved to the extent which is comparable with that of the mechanical gears.
Torque density has always been an important performance indicator to measure the performance of magnetic gears. In order to improve the torque density of the magnetic gears, many experts have been researching the topological structures of magnetic gears deeply. Currently, the magnetic gears are mainly classified into two categories: radial magnetic gear and axial magnetic gear. The radial magnetic gear means a magnetic gear of which the air-gap magnetic field distributes radially, and the topological structure of the radial magnetic gear is distributed with an inner rotor, a magnetic regulation ring and an outer ring from the inside out. The magnetic regulation ring located between the inner rotor and the outer rotor brings great trouble for designing, manufacturing, fixing and supporting the structure of the magnetic regulation ring, since each of the magnetic regulation iron cores of the magnetic regulation ring of the magnetic gear cannot be short-connected together in order to improve the performance of the magnetic regulation performance of the iron core. In order to decrease eddy-current loss, two end caps respectively on the left and right of the magnetic regulation ring are added with insulating mats, and even fixture bolts are considered to be added with insulating devices. Furthermore, since the iron cores of the magnetic regulation ring are independent, and the magnetic fields produced by the permanent magnets of the inner rotor and outer rotor work on the still magnetic regulation ring, therefore, the issues such as the rigidity of the mounted iron core structure and avoiding the position shift of the iron core should be considered. Technical solutions of the prior art remedy the above mentioned issues, however, the technical solutions improve the complexity of the structure, some of them even sacrifice the performance of the magnetic gear. Another kind of axial magnetic gear means magnetic gear of which the air-gap magnetic field distributes axially. The magnetic gear is axially distributed with a slow disk composed of a slow disk iron core and a slow disk permanent magnet, a stator composed of magnetic regulation iron blocks, and a fast disk composed of a fast disk permanent magnet and a fast disk iron core from left to right. However, the above-mentioned radial magnetic gear and axial magnetic gear possess a sole magnetic circuit, which is either radial or axial, and the design and the manufacturing of the magnetic regulation mechanism of the radial magnetic gear are very troublesome.